The present invention relates to a method of manufacturing a cathode-ray tube and, more particularly, to a method of coating a film forming liquid on an inner surface of a faceplate when a phosphor screen is formed on the inner surface of the faceplate.
In order to form a phosphor screen on an inner surface of a faceplate of a conventional cathode-ray tube, various film forming liquids are coated on the inner surface of the faceplate and are dried. For example, in a black matrix tube manufactured for improving brightness and contrast of the color picture tube, a dot or stripe pattern made of a polymer material is formed on the inner surface of the faceplate. Subsequently, a graphite suspension or slurry is coated on the dot or stripe pattern. The polymer material constituting the pattern is removed together with the overlying graphite film by a stripping agent or the like. Three color phosphors are coated along the window pattern from which the polymer material is removed.
In this case, the graphite suspension is coated on the inner surface of a faceplate 1 in a manner shown in FIG. 1. The inner surface of the faceplate 1 faces downward while the faceplate 1 is being rotated. A supply nozzle 2 sprays the graphite suspension at a large angle with respect to a normal to the inner surface, as described in Japanese Patent Publication No. 50-25496.
However, when the graphite film is formed on the inner surface of the faceplate 1 according to this method, irregular coating occurs especially at a spray start portion, as shown in FIG. 2. The jet is gradually sprayed along the inner surface of the faceplate while the faceplate is being rotated, so that a boundary between the first coated portion and a noncoated portion in front of the first coated portion does not change until the faceplate revolves once. The boundary portion becomes hardened during the time the faceplate revolves. When a jet is sprayed at the boundary portion again, a thickness of the boundary portion is increased. As a result, the boundary portion appears as an involute curve.
Another problem is presented by this conventional method. Since the graphite particles are flake-like particles, they are aligned along a graphite suspension flow. The resultant film has different glossy portions in accordance with the direction of the jet flow. At a boundary portion between a film portion obtained by first spraying of the suspension jet on the inner surface portion of the faceplate and a film portion obtained by subsequent spraying, the jet flow spreads, resulting in irregular coating.